Extractive distillation of crude alcohol product

Abstract

Recovery of ethanol from a crude ethanol product obtained from the hydrogenation of acetic acid using an extractive distillation column. The column yields a residue that comprises ethanol, acetic acid, and the extractive agent. The extractive agent may be water and may be separated from the residue and returned to the extractive distillation column.

We claim: 
     
       1. A process for producing ethanol, comprising:
 hydrogenating acetic acid from an acetic acid feed stream in a reactor to form a crude ethanol product comprising ethanol, ethyl acetate, and acetic acid, wherein the crude ethanol product comprises at least a portion of the one or more extractive agents; 
 separating at least a portion of the crude ethanol product in a first column in the presence of the one or more extractive agents into a first distillate comprising ethyl acetate, and a first residue comprising ethanol, acetic acid, and the one or more extractive agents, wherein the first residue comprises less than 1 wt. % ethyl acetate; 
 separating the first residue in a second column into a second distillate comprising ethanol and the one or more extractive agent, and a second residue comprising acetic acid; 
 separating the second distillate in a third column into a third distillate comprising ethanol, and a third residue comprising the one or more extractive agent; and 
 recovering at least a portion of the one or more extractive agent from the third residue. 
 
     
     
       2. The process of  claim 1 , wherein the one or more extractive agents comprise water. 
     
     
       3. The process of  claim 1 , wherein the one or more extractive agents are selected from a group consisting of water, dimethylsulfoxide, glycerine, diethylene glycol, 1-naphthol, hydroquinone, N,N′-dimethylformamide, 1,4-butanediol, ethylene glycol-1,5-pentanediol; propylene glycol-tetraethylene glycol-polyethylene glycol; glycerine-propylene glycol-tetraethylene glycol-1,4-butanediol, ethyl ether, methyl formate, cyclohexane, N,N′dimethyl-1,3-propanediamine, N,N′-dimethylethylenediamine, diethylene triamine, hexamethylene diamine, 1,3-diaminopentane, and alkylated thiopene, dodecane, tridecane, tetradecane, chlorinated paraffins, and mixtures thereof. 
     
     
       4. The process of  claim 1 , wherein at least 90% of the ethyl acetate in the crude ethanol product is recovered through the first distillate. 
     
     
       5. The process of  claim 1 , wherein the mass flow ratio of the one or more extractive agents to the crude ethanol product is from 2:1 to 1:15. 
     
     
       6. The process of  claim 1 , wherein the first residue comprises from 1 wppm to 800 wppm ethyl acetate. 
     
     
       7. The process of  claim 1 , wherein the first distillate further comprises less than 0.2 wt. % acetic acid. 
     
     
       8. The process of  claim 1 , wherein the first distillate further comprises from 0.1 to 30 wt. % acetaldehyde and from 0.1 to 30 wt. % acetal. 
     
     
       9. The process of  claim 1 , wherein the one or more extractive agents are co-produced in the reactor. 
     
     
       10. A process for producing ethanol, comprising:
 hydrogenating acetic acid from an acetic acid feed stream in a reactor to form a crude ethanol product comprising ethanol, ethyl acetate, and acetic acid wherein the crude ethanol product comprises at least a portion of the one or more extractive agents; 
 separating at least a portion of the crude ethanol product in a first column in the presence of the one or more extractive agents into a first distillate comprising ethyl acetate, and a first residue comprising ethanol, acetic acid, and the one or more extractive agents, wherein the first residue comprises less than 1 wt. % ethyl acetate; 
 separating the first residue in a second column into a second distillate comprising ethanol, and a second residue comprising the one or more extractive agents and acetic acid, and 
 recovering the one or more extractive agents from the second residue. 
 
     
     
       11. The process of  claim 10 , further comprising separating the second residue to recover the one or more extractive agents and recycling the recovered one or more extractive agents to the first column. 
     
     
       12. The process of  claim 10 , wherein the one or more extractive agents comprise water. 
     
     
       13. The process of  claim 10 , wherein the one or more extractive agents are selected from the group consisting of water, dimethylsulfoxide, glycerine, diethylene glycol, 1-naphthol, hydroquinone, N,N′-dimethylformamide, 1,4-butanediol, ethylene glycol-1,5-pentanediol; propylene glycol-tetraethylene glycol-polyethylene glycol; glycerine-propylene glycol-tetraethylene glycol-1,4-butanediol, ethyl ether, methyl formate, cyclohexane, N,N′dimethyl-1,3-propanediamine, N,N′-dimethylethylenediamine, diethylene triamine, hexamethylene diamine, 1,3-diaminopentane, and alkylated thiopene, dodecane, tridecane, tetradecane, chlorinated paraffins, and mixtures thereof. 
     
     
       14. The process of  claim 10 , wherein at least 90% of the ethyl acetate in the crude ethanol product is recovered through the first distillate. 
     
     
       15. The process of  claim 10 , wherein the second distillate comprises from 70 wt. % to 99.9 wt. % ethanol, from 0.1 wt. % to 30 wt. % water, and less than 10 wt. % ethyl acetate. 
     
     
       16. The process of  claim 10 , wherein the second distillate is substantially free of acetic acid. 
     
     
       17. The process of  claim 10 , further comprising separating the second distillate in a third column into a third distillate comprising ethanol, and a third residue comprising the one or more extractive agents. 
     
     
       18. A process for producing ethanol, comprising the steps of:
 providing a crude ethanol product comprising ethanol, acetic acid, and ethyl acetate wherein the crude ethanol product comprises at least a portion of the one or more extractive agents; 
 separating at least a portion of the crude ethanol product in a first column in the presence of the one or more extractive agents into a first distillate comprising ethyl acetate, and a first residue comprising ethanol, acetic acid, and the one or more extractive agents, wherein the first residue comprises less than 1 wt. % ethyl acetate; 
 separating the first residue in a second column into a second distillate comprising ethanol and one or more extractive agent, and a second residue comprising acetic acid; 
 separating the second distillate in a third column into a third distillate comprising ethanol, and a third residue comprising the one or more extractive agent; and 
 recovering the one or more extractive agent from the third residue. 
 
     
     
       19. The process of  claim 18 , wherein the first residue comprises from 1 wppm to 800 wppm ethyl acetate. 
     
     
       20. The process of  claim 18 , wherein the one or more extractive agents are selected from a group consisting of water, dimethylsulfoxide, glycerine, diethylene glycol, 1-naphthol, hydroquinone, N,N′-dimethylformamide, 1,4-butanediol, ethylene glycol-1,5-pentanediol; propylene glycol-tetraethylene glycol-polyethylene glycol; glycerine-propylene glycol-tetraethylene glycol-1,4-butanediol, ethyl ether, methyl formate, cyclohexane, N,N′dimethyl-1,3-propanediamine, N,N′-dimethylethylenediamine, diethylene triamine, hexamethylene diamine, 1,3-diaminopentane, and alkylated thiopene, dodecane, tridecane, tetradecane, chlorinated paraffins, and mixtures thereof.